A New Technology for 3-D Seismic Exploration and Development of Fractured Tight Gas Reservoirs*

By

James J. Reeves¹

Search and Discovery Article #40177 (2005)

Posted November 10, 2005

*Oral Presentation at Rocky Mountain Section AAPG Annual Meeting, Jackson, Wyoming, September 24-26, 2005. Appreciation is expressed to Lyn George, Technical Program Chair, and Don French, for encouraging the author to submit this presentation.

Click to view presentation in PDF format.

¹GeoSpectrum, Inc, P.O. Box 3399, 214 W. Texas, Midland, TX 79701, phone: 432 686 8626 ([email protected])

Abstract 

A 3D seismic exploration method for fractured tight gas reservoirs is developed in a study conducted for the U. S. Department of Energy. The interpretation methodology is based on three principal reservoir attributes--fracture density, clay volume, and gas content.  

Seismic lineament analysis is used to map lineaments through the reservoir zone using horizon slices and time slices. We interpret that in a probabilistic sense where lineaments swarm and cluster together is where reservoir fractures are most likely to be found. Leads identified using lineament density are further screened using rock typing to identify reservoir that is more likely to fracture. A collocated cokriged clay volume map using near trace seismic amplitude (an AVO attribute) is used to identify reservoir having low clay that is interpreted to be more brittle and more prone to fracturing. Fractured reservoir and good reservoir rock do not necessarily make a drillable prospect, as reservoir fractures may provide a plumbing system to both water and gas. For prospect development a gas sensitive phase gradient AVO attribute is used to further screen the leads to insure that gas is present.  

In a gas field previously plagued with poor drilling results in the San Juan Basin of New Mexico, four new wells were spotted using the methodology and recently drilled. The wells have estimated best of 12-months production indicators of 2106, 1652, 941, and 227 MCFGPD.

Location map, San Juan Basin (after Peterson et al., 1965).

Type log, Cretaceous Greenhorn – Burro Canyon interval (after Whitehead, 1993).

Dakota production trends (after C.F. Head, 2001), seismic lineaments, and borehole image data.

References 

Head, C.F., 2001, Dakota interval production, San Juan Basin, New Mexico: Burlington Resources, Farmington, New Mexico, Proprietary Map, June, 2001.

Peterson, James A., Allan J. Loleit, Charles W. Spencer , and Richard A. Ullrich, 1965, Sedimentary history and economic geology of San Juan Basin: AAAPG Bulletin v. 49, p. 2076-2119.

Whitehead, N.H., III, 1993, San Juan plays; Dakota and Dakota-Morrison formations, in C.A. Hjellming, ed., Atlas of major Rocky Mountain gas reservoirs: New Mexico Bureau of Mines and Mineral Resources, p. 133-136.